At present, a digital television Conditional Access System (CAS) is a core link in a digital television service chain, which implements user entitlement management functions such as product segmentation, data encryption, authorized access control of digital television service data, thereby ensuring that the user legally watches, through a single-item wired network, encrypted and paid television programs provided by a digital television provider; and the CAS is also a technical basis for digital television providers to charge.
The existing digital television CAS generally performs scrambling protection on original digital television data by using a three-layer key (or multiple-layer key) system. A conventional three-layer key system includes a Control Word (CW), a Service Key (SK), and a Personal Distribute Key (PDK). A front-end scrambling system performs scrambling on audio/video and data services of the digital television by using the CW; meanwhile, the front-end digital television CAS performs scrambling protection on the CW through the SK, to generate an Encrypted Control Word (ECW), which in turn, is protected by the PDK to generate a user Entitle Manage Message (EMM). The user EMM is then transmitted to a receiving module of a set top box.
In a conventional CA card authentication, a software impulse at a digital television terminal receives a data packet. A digital television filter module performs filtering processing on the data packet to obtain the user EMM and an Entitlement Control Message (ECM). The obtained user EMM and ECM are sent to the CA card. The CA card performs descrambling on the user EMM by using the PDK to acquire SK information, and then performs descrambling on the ECM by using the SK to acquire the ECW, performs descrambling on the ECW to acquire the CW, encrypts the CW, and transmits the encrypted CW to a machine-card communication module on the digital television. The machine-card communication module stores the CW in plaintext into a Random Access Memory (RAM) of the digital television. A digital television master chip then reads the CW for descrambling and decoding.
In such conventional authentication, a unique identifier of the user is provided by the CA card, and the CA card frequently communicates with the set top box. If hackers crack the password, a risk that an algorithm is stolen exists. Additionally, upgrading in the conventional authentication is not only inconvenient, but also cause a high cost.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.